Obviously, the outside annual climate change caused either by a major solar input during the hottest period or by a temperature drop during the coldest period leads to discomfort in inside buildings. This effect can be reduced by storing heat transmitted in phase change materials (PCM) as latent heat, in order to ensure a good situation of thermal comfort during all months of the year. In this work, thermal behavior of two roofing systems is studied. One roof is constituted only by usual materials in building. In the other, two phase change materials (PCM) are introduced according to three configurations. Study is interested to assess incorporation effect of two PCMs within the roof and to evaluate the optimum locations to reduce the energy consumption of air-conditioned room. Mono-dimensional numerical model validated analytically and experimentally, is used to carry out a parametric analyzes to determine characteristics of the layers in which the roofs are formed regardless of external climate effect. Numerical calculations are performed for three configurations of roof. Results show that insertion of phase change materials in roof provides best energy consumption saving regardless annual climate change. Generally, the three configurations lead to different results, depending on the combination of PCMs. This difference becomes less important when selection of PCMs take account the thermal comfort level and temperatures of hottest and coldest periods.